Analysis of performance of two-stage screw compressor under various operating conditions

Abstract

The screw compressor has a promising application in the process industry due to its appropriate pressure and flow rate. In this paper, a mathematical model of a two-stage oil-free screw compressor is developed to simulate the working process under various operating conditions. The results show that the interstage pressure of the two-stage oil-free screw compressor is built automatically depending on the equal mass flow rate of each stage. It increases with the suction pressure, discharge pressure, and clearance, but decreases with rotating speed. Although the power consumption of the 2nd stage decreases with the suction pressure, the power consumption of the whole compressor always increases with the suction pressure, discharge pressure, rotating speed, and clearance. The volumetric efficiency increases with the suction pressure and rotating speed, but decreases with the discharge pressure and clearance for each stage. The indicated efficiency increases with the rotating speed but decreases with the clearance. A maximum indicated efficiency is found. The volumetric and indicated efficiency of the 2nd stage is more sensitive to the operating condition than that of the 1st stage.